JP2009072420A - Absorbent article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an absorbent article hardly generating return of wetness or leakage of liquid, and hardly causing a sense of discomfort from the swelling of water-absorbent polymer. <P>SOLUTION: The absorbent article 1 has an absorber 3 including the water-absorbent polymer 10 whose liquid permeation speed under pressure of 2.0 kPa is at least 50 mL/min and the quantity of absorption under pressure of 2.0 kPa is less than 25 g/g. In one embodiment, the absorber 3 comprises an upper absorbent layer 31 made of a fiber blend of the water-absorbent polymer 10 and a fibrous substance, and a lower absorbent layer 32 disposed on the non-skin contact side of the upper absorbent layer 31. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an absorbent article including an absorbent body that includes a water-absorbing polymer.

  Absorbent articles such as disposable diapers, sanitary napkins, and incontinence pads widely use water-absorbing polymers for the purpose of absorbing bodily fluids such as urine. Examples of the water-absorbing polymer include a crosslinked polyacrylic acid partial neutralized product, a hydrolyzate of starch-acrylic acid graft polymer, a saponified vinyl acetate-acrylic acid ester copolymer, an acrylonitrile copolymer or an acrylamide copolymer. Polymer hydrolysates or cross-linked products thereof, and cationic monomers are used as main raw materials.

By using a water-absorbing polymer together with fiber materials such as pulp fiber, the absorption performance is improved while suppressing the thickness of the absorber, or a phenomenon called wetback where the liquid once absorbed by the absorber returns to the surface and becomes sticky Can be reduced.
However, when the proportion of the water-absorbing polymer is increased, so-called gel blocking, in which the liquid passage in the absorbent body is blocked by the water-absorbing polymer swollen by the absorption of the liquid, tends to occur. This gel blocking, for example, shows good liquid absorbability at the time of the first body fluid absorption, but the liquid absorbability is greatly reduced at the second and subsequent body fluid absorption, and the surface of the absorber is not absorbed. Problems such as liquid leakage occur due to the liquid flowing through.

Patent Document 1 proposes an absorptive member in which a water-absorbing polymer can be present at a high concentration in a predetermined region by using a water-absorbing polymer having a high absorption amount and liquid permeability under pressure. Has been.
However, water-absorbing polymers with high absorption under pressure swell and increase in volume even when pressure is applied during wearing of the absorbent article, so the thickness of the absorbent article increases and the wearer feels uncomfortable. May give.

Japanese National Publication No. 9-510889

  Accordingly, an object of the present invention is to provide an absorbent article that hardly causes wetback and liquid leakage, and that does not easily cause discomfort due to swelling of the water-absorbing polymer.

  The present invention provides an absorbent body comprising a water-absorbing polymer having a flow rate under pressure at 2.0 kPa of 50 ml / min or more and an absorption amount under pressure at 2.0 kPa of less than 25 g / g. The object is achieved by providing an absorbent article provided.

  The absorbent article of the present invention is less susceptible to wetback and liquid leakage, and is less likely to cause discomfort due to swelling of the water-absorbing polymer.

Hereinafter, the present invention will be described based on preferred embodiments thereof.
The disposable diaper as 1st Embodiment of this invention is shown by FIG. 2 is a cross-sectional view taken along line II in FIG. In FIG. 2, the portion that was broken in FIG. 1 is shown in a state where it is not broken.

  The diaper 1 of the first embodiment includes a liquid-permeable top sheet 2, a vertically long absorbent body 3 including a water-absorbing polymer 10, and a liquid-impermeable or water-repellent and moisture-permeable back sheet 4. And is formed substantially vertically long. The absorbent body 3 is disposed between the top sheet 2 and the back sheet 4 with its longitudinal direction coinciding with the longitudinal direction L of the diaper 1.

The absorbent body 3 includes an upper absorbent layer 31 composed of a fiber mixture 33 of the water absorbent polymer 10 and hydrophilic fibers, and a lower absorbent disposed on the non-skin contact surface side (the back sheet 4 side) of the upper absorbent layer 31. Layer 32. The lower absorbent layer 32 in the present embodiment is composed of a fiber mixture 34 of the second water-absorbing polymer 11 having a physical property different from that of the water-absorbing polymer 10 and a fibrous material.
Moreover, the whole fiber mixture 33 (upper absorbent layer 31) or a portion excluding both end faces in the longitudinal direction is covered with a covering sheet (not shown). The lower absorbent layer 32 is also covered with a covering sheet (not shown), or the entire portion except for both end surfaces in the longitudinal direction. The covering sheet is a liquid-permeable sheet for maintaining the shape retention of the mixtures 33 and 34 and preventing the water-absorbing polymer 10 and the second water-absorbing polymer 11 from falling off. As the covering sheet, for example, paper such as tissue paper, various non-woven fabrics, perforated films and the like can be used.

  The absorber 3 is characterized by a water-absorbing polymer 10 contained therein. The water-absorbing polymer 10 is characterized in that the liquid passing rate under pressure is high, but the absorbed amount under pressure is suppressed to less than a predetermined value.

Hereinafter, the water-absorbing polymer 10 will be described.
The water-absorbing polymer 10 has a liquid flow rate under pressure of 2.0 kPa of 50 ml / min or more, and when the object of absorption is a low-viscosity liquid such as urine (generally having a viscosity of 10 mPa or less), preferably 50 to 200 ml / min, more preferably 60 to 150 ml / min. Here, the load of 2.0 kPa substantially corresponds to the body pressure applied to the absorbent body when the absorbent article is worn.

  When the value of the water-absorbing polymer liquid flow rate is less than 50 ml / min, the water-absorbing polymers saturated and swollen by the liquid absorption adhere to each other under load, and the passage of the liquid is prevented, and gel blocking occurs. Cheap. As a result, the remaining surface liquid tends to increase, which tends to cause an increase in skin troubles due to adherence of excrement to the skin. Moreover, as shown below, when a large amount of excrement or excretion speed is high, or when the absorber is thinned, no leakage occurs. By making the liquid-absorbing polymer 10 flow rate within the above range, gel blocking is less likely to occur, and when a large amount of excreta is excreted at a time, it is found in examples of older infants or adults. Thus, when the excretion rate is fast, even when the absorber is further thinned, the liquid can be quickly transferred from a portion close to the wearer's skin in the absorber to a portion far away from the wearer, so that liquid leakage is less likely to occur. .

The larger the value of the liquid flow rate, the better from the viewpoint of preventing the occurrence of gel blocking. However, when the absorption target is a low-viscosity liquid such as urine, the value of the liquid flow rate exceeds 200 ml / min. In this case, a thin absorbent body (especially, having a pulp basis weight of 300 g / m ² or less, more preferably 250 g / m ² or less, and also 200 g / m ² or less, or absorption, especially with few hydrophilic fibers such as pulp. When the body thickness is less than 4 mm), the liquid cannot be sufficiently fixed in the absorbent body, and the end of the absorbent body is liable to leak, or the crotch part in the standing position, the stomach side in the lying state, From this point of view, the upper limit value of the (preferred) preferred range is determined from the viewpoint of liquid accumulation on the surface of the diaper where the liquid easily flows. It was.

In addition, the preferable range of the liquid passing speed is an appropriate range for using the water-absorbing polymer most efficiently when the object of absorption is a low-viscosity liquid such as urine. Of course, even in the case of an absorbing polymer having a liquid flow rate exceeding 200 ml / min, the performance as an absorber can be secured by using a large amount of pulp or the like, but the function of preventing gel blocking is assumed by the pulp. Therefore, it is not always necessary to bear the water-absorbing polymer alone.
When the water-absorbing polymer of the present invention is used for a highly viscous liquid such as blood (generally having a viscosity of 50 mPa or more), the liquid passing rate under pressure at 2.0 kPa is preferably 80 to 1000 ml / min, more preferably 120-800 ml / min.

  The liquid passing rate under pressure is measured using a measuring method and a measuring apparatus described in JP-A-2003-235889. Specifically, the flow rate under pressure at 2.0 kPa is measured by the following procedure. These measurements are performed at 23 ± 2 ° C. and a relative humidity of 50 ± 5%, and the sample is stored after being stored in the same environment for 24 hours or more.

(Measurement method of liquid flow rate under pressure)
In a 100 mL glass beaker, a sufficient amount of physiological saline (0.9 wt% sodium chloride water) to swell the measurement sample water-absorbing polymer 0.32 ± 0.005 g, for example, the saturated absorption amount of the water-absorbing polymer Immerse it in 5 times more saline and leave it for 30 minutes.
Separately, at the lower end of an opening of a vertically standing cylinder (inner diameter 25.4 mm), a wire mesh (mesh opening 150 μm, biocolumn sintered stainless steel filter 30SUS sold by Sansho Co., Ltd.) and a capillary (with an inner diameter of 2 mm) ( A filtration cylindrical tube having an inner diameter of 4 mm and a length of 8 cm) is prepared, and the contents of the beaker including the swollen measurement sample are put into the cylindrical tube with the cock closed. Next, a cylindrical rod having a diameter of 2 mm with a wire mesh having an opening of 150 μm and a diameter of 25 mm is inserted into the filtration cylindrical tube so that the wire mesh and the measurement sample are in contact with each other. Place a weight so that the load of. After standing in this state for 1 minute, the cock is opened to flow the liquid, and the time until the liquid level in the filtration cylindrical tube reaches the 40 mL scale line from the 60 mL scale line (that is, 20 mL of liquid passes) (T ₁ ) (Seconds). Using the measured time T ₁ (seconds), the flow rate at 2.0 kPa is calculated from the following equation. In the formula, T ₀ (seconds) is a value obtained by measuring the time required for 20 ml of physiological saline to pass through the wire mesh without putting the measurement sample in the filtering cylindrical tube.
Flow rate (ml / min) = 20 × 60 / (T ₁ −T ₀ )
The value obtained by the above formula is divided by the thickness of the swollen water-absorbing polymer layer in the cylinder, and converted to a value per 20 mm to obtain a liquid passing speed under pressure. The measurement was performed 5 times (n = 5), the values at each of the upper and lower points were deleted, and the average value of the remaining three points was taken as the measured value.
A more detailed method for measuring the flow rate is described in paragraphs 0008 and 0009 of JP-A-2003-235889. The measuring device is described in FIGS. 1 and 2 of the publication.

Further, the water-absorbing polymer 10 has an absorption amount under pressure at 2.0 kPa of less than 25 g / g. The amount of absorption under pressure is a measure of how much the water-absorbing polymer can be absorbed in a state where pressure is applied to the absorbent body by wearing the absorbent article.
When the absorption amount of the water-absorbing polymer is 25 g / g or more, the amount of the water-absorbing polymer necessary for maintaining the absorption capacity of the entire absorbent article at a predetermined level is theoretically small. However, if the absorption of the absorber is suppressed and the water-absorbing polymer absorbs water to the maximum extent, the particles of each water-absorbing polymer increase, leading to a feeling of strangeness during wearing.
Moreover, when the average particle diameter of the swollen gel becomes too large, the packing property of the gel is deteriorated. In this case, the increase in the gel interstitial water increases from the stage where the maximum absorption amount of the water-absorbing polymer is exceeded, and there is a concern about the increase in the liquid return amount associated therewith.
Further, the absorption performance of the absorbent article is greatly affected not only by the overall absorption capacity but also by the absorption rate. If the absorption amount of the water-absorbing polymer is 25 g / g or more, there is a problem that if the amount of the water-absorbing polymer is decreased based on the water absorption amount, the absorption rate is insufficient.

On the other hand, when the amount of absorption under pressure is extremely low, i.e., less than 12 g / g, an absorbent article to be used in a state where pressure is not applied so much, for example, a pant diaper worn by an older infant, especially It can be used as training pants used almost during the day and as diapers for low-age infants with low urination.
Furthermore, in order to supplement the absorption capacity, other absorbent materials such as pulp may be supplemented as appropriate. Various fiber materials such as pulp, rayon, and synthetic fibers, and various foams such as cellulose, urethane, and polyester have a function of suppressing the direct application of pressure to the water-absorbing polymer. Helps to work efficiently.
When making the diaper thin and light from the viewpoint of portability and wearability, the absorption capacity under pressure of the water-absorbing polymer used in the present invention is 12 g / g or more and 25 g / g in order to achieve compatibility with the absorption performance. It is preferably less than g, more preferably 15 g / g or more and less than 25 g / g.

Alternatively, in the case of using a water-absorbing polymer having a polyamino acid as the main chain, the performance derived from the chemical structure of the amino acid, which works effectively in providing a biodegradable absorbent article, is preserved during long-term storage. It may work as a disadvantage in terms of stability. Therefore, it is preferable to develop a long-term stable absorption performance by increasing the degree of crosslinking and suppressing the amount of absorption under pressure.
From the viewpoints of suppressing the increase in gel interstitial water and the accompanying increase in liquid return due to the expression of stable absorption performance and reduction in discomfort, the increase in the average particle size of the swollen gel, It is preferable that it is 25 g / g, More preferably, it is 14-22 g / g.

(Measurement method of absorption under pressure)
The amount of absorption under pressure is measured using a measuring method and measuring apparatus described in JP-A-2003-235889. Measurement is performed as follows in an environment of 25 ± 2 ° C. and a relative humidity of 50% ± 5%.
That is, a sample (water-absorbing polymer) 0.10 g was weighed in a cylindrical plastic tube (inner diameter 30 mm, height 60 mm) with a nylon mesh (JIS Z8801-1: 2000) having a mesh size of 63 μm attached to the bottom surface, and the cylindrical plastic tube Set the sample vertically on the nylon mesh so that the sample is almost uniform in thickness, and insert a weight of 29.5 mm in outer diameter and 22 mm in thickness into the cylindrical plastic tube so that the pressure of 2.0 kPa is applied to the sample To do. The weight of the cylindrical plastic tube and the weight is measured in advance.
Next, a cylindrical plastic tube containing a sample and a weight in a petri dish (diameter: 120 mm) containing 60 ml of physiological saline is vertically immersed with the nylon mesh side as the bottom surface. At this time, the cylindrical plastic tube is immersed to the depth of the bottom of the petri dish.
After 60 minutes, pull up the cylindrical plastic tube containing the sample and weight from the water, weigh it, subtract the weight of the cylindrical plastic tube and the weight, and calculate the weight of the physiological saline absorbed by the sample. To do. A value obtained by multiplying the weight of the absorbed physiological saline by 10 is defined as an absorbed amount under pressure (g / g).

  By using a water-absorbing polymer in which the above-mentioned two characteristics (the liquid flow rate under pressure at 2.0 kPa and the amount of water absorbed under pressure at 2.0 kPa) are adjusted to the above-described ranges, respectively, are used as constituents of the absorber. In both the first liquid absorption and the second and subsequent liquid absorption, the liquid can be quickly absorbed, the liquid return is small and leakage is not likely to occur, and an absorbent body that is less susceptible to discomfort due to swelling of the water-absorbing polymer can be obtained. .

In the case where the lower absorbent layer 32 has a function as a liquid holding layer, it is preferable that the second water-absorbing polymer 11 to be used is a water-absorbing polymer whose liquid passing rate under pressure is less than 50 ml / min. In this case, since the diffusion in the lower absorption layer 32 is suppressed, the absorption capacity of the water-absorbing polymer 11 can be used efficiently, the capacity of the entire absorber can be increased, and the liquid return and leakage can be suppressed. . The uptake of liquid into the absorbent article is designed to be compensated with the diffusibility of the upper absorbent part.
In addition, as can be seen in sanitary napkins, when the upper absorbent part is smaller than the lower absorbent part, the upper absorbent part can be placed on the body by reducing the amount of the second water-absorbing polymer in contact with the upper absorbent part. It is possible to suppress the occurrence of a sense of incongruity due to close contact with the surface. In the same way, a different third water-absorbing polymer may be used in the lower absorbent portion.
Or the structure like a leak-proof wall can be made by using a water-absorbing polymer having a high absorption amount under pressure at the peripheral edge of the lower absorbent portion.
Of course, depending on the setting of the absorption capacity, the water absorbent polymer 10 used in the upper absorbent part may be used in the lower absorbent part, or the water absorbent polymer may not be arranged.

As the water-absorbing polymer in which the above-mentioned two characteristics (the liquid flow rate under pressure at 2.0 kPa and the water absorption amount under pressure at 2.0 kPa) are in the above-mentioned ranges, for example, the following are preferably used: Can do.
(1) After polymerizing a polymerizable monomer, a crosslinking material is added to form a bridge structure, and surface crosslinking is further performed.
(2) A polyamino acid main chain. Here, the polyamino acid is an amino acid homopolymer, a copolymer of an amino acid and another monomer component, or a copolymer of a plurality of types of amino acids. The main chain is a portion excluding the crosslinked portion of the polymer.
(3) A surface treatment applied to the water-absorbing polymer of (1) or (2). In addition, the following can be used as a surface treating agent. For example, aluminum sulfate, potassium alum, ammonium alum, sodium alum, (poly) aluminum chloride, polyvalent metal compounds such as hydrates thereof; polycation compounds such as polyethyleneimine, polyvinylamine, polyallylamine; silica, alumina, Inorganic fine particles such as titanium oxide, zinc oxide, bentonite; and the like may be used, and only one of these may be used, or two or more may be used in combination. Among these, inorganic fine particles such as silica are preferable in terms of improving the water absorption speed and liquid permeability.

The water-absorbing polymer (1) will be described.
Examples of the polymerizable monomer include various vinyl monomers that are water-soluble and have a polymerizable unsaturated group. Specifically, the olefinic unsaturated carboxylic acid or a salt thereof, an olefinic unsaturated carboxylic acid ester, Olefinically unsaturated sulfonic acid or its salt, olefinically unsaturated phosphoric acid or its salt, olefinically unsaturated phosphate ester, olefinically unsaturated amine, olefinically unsaturated ammonium salt, and / or olefinically unsaturated amide, etc. The vinyl monomer which has the following polymerizable unsaturated group is illustrated.

  As the olefinic unsaturated carboxylic acid or a salt thereof, an unsaturated carboxylic acid such as acrylic acid, methacrylic acid, maleic acid or fumaric acid and / or an alkali metal salt or an ammonium salt thereof is used. Acid, alkali metal acrylate (sodium salt, potassium salt, etc.) and / or ammonium acrylate are used.

Examples of the olefinic unsaturated carboxylic acid ester include methoxypolyethylene glycol (meth) acrylate, phenoxypolyethyleneglycol (meth) acrylate, hydroxyethyl (meth) acrylate, and the like, and examples of the olefinic unsaturated sulfonic acid or a salt thereof include vinyl. Anionic unsaturation such as sulfonic acid, allyl sulfonic acid, styrene sulfonic acid, 2- (meth) acrylamido-2-methylpropanesulfonic acid, 2- (meth) acryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid A monomer and / or its salt are mentioned.
Examples of the olefinically unsaturated phosphoric acid or salt thereof include (meth) acryloyl (poly) oxyethylene phosphate ester and / or an alkali salt thereof. Examples of the olefinically unsaturated amine include N, N-dimethylaminoethyl. Cations such as (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide and / or quaternary salts thereof Olefinically unsaturated monomers, examples of olefinically unsaturated ammonium salts include (meth) acryloyloxyethylenetrimethylammonium halogen salts, and examples of olefinically unsaturated amides include (meth) acrylamide, methyl ( (Meth) acrylamide, N-ethyl (meth) Acrylamide, N- (meth) acrylamide, N- isopropyl (meth) acrylamide, N, N- dimethyl (meth) (meth) acrylamide derivatives and vinyl methylacetamide acrylamide and the like.
Specific examples of other monomers include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, polyethylene glycol mono (meth) acrylate, vinylpyridine, N- Nonionic hydrophilic group-containing unsaturated monomers such as vinylpyrrolidone, N-acryloylpiperidine, N-acryloylpyrrolidine, N-vinylacetamide and the like can be mentioned.

When using a polymerizable monomer, it is used alone or as a mixture of two or more. Of these, olefinically unsaturated carboxylic acids and / or alkali salts thereof are preferably used in the present invention, more preferably acrylic acid, methacrylic acid and / or alkali metal salts or alkaline earth metal salts thereof. It is done.
Moreover, when a polymerizable monomer is solid at normal temperature, it can be used as an aqueous solution. In this case, the concentration of the polymerizable monomer in the aqueous solution is preferably 10% by weight or more, more preferably 20% by weight or more, and still more preferably 30% by weight or more in the entire aqueous solution from the viewpoint of productivity. The water-soluble polymerizable monomer can be used in combination with a water-insoluble polymerizable monomer that can be copolymerized therewith. Examples of the water-insoluble polymerizable monomer include unsaturated carboxylic acid ester monomers such as acrylic acid, methacrylic acid, maleic acid and fumaric acid having an alkyl group having 1 to 18 carbon atoms, and styrene. In this case, the water-soluble polymerizable monomer is preferably contained in the total polymerizable monomer in an amount of 50% by weight or more, particularly 70% by weight or more.

Examples of the hydrophobic organic solvent inert to the polymerization used in the production of the water-absorbing polymer (1) include fats such as n-pentane, cyclopentane, n-hexane, cyclohexane, n-heptane, and methylcyclohexane. Aliphatic hydrocarbons such as aromatic hydrocarbons such as aromatic hydrocarbons, benzene and toluene, aliphatic alcohols having 4 to 6 carbon atoms such as n-butyl alcohol and n-amyl alcohol, aliphatic ketones such as methyl ethyl ketone, and aliphatic esters such as ethyl acetate Examples thereof include silicone oil and fragrance. In use, it can be used as one or a mixture of two or more. Moreover, the usage-amount of the said hydrophobic organic solvent becomes like this. Preferably it is 50-500 weight part with respect to 100 weight part of water-soluble polymerizable monomers or its aqueous solution, More preferably, it is 100-500 weight part.
In addition to the hydrophobic solvent, an amphiphilic solvent may be used for the production of the water-absorbing polymer. The amount of the amphiphilic solvent used is preferably a total amount with the hydrophobic organic solvent and up to 500 parts by weight with respect to 100 parts by weight of the polymerizable monomer. Examples of the amphiphilic solvent include alcohols such as methanol, ethanol, propanol and 2-propanol, ketones such as acetone, and ethers such as tetrahydrofuran and dioxane.

  Examples of dispersants that can be used during polymerization include: (a) carboxylic acid derivatives; N-acyl aspartic acid or N-acyl glutamic acid and / or salts thereof, polyoxyethylene alkyl as anionic surfactants Ether carboxylic acid and / or salt thereof, fatty acid soap. (B) Sulfuric acid derivative; alkyl sulfuric acid and / or salt thereof, polyoxyethylene alkyl ether sulfuric acid and / or salt thereof. (C) Sulfonic acid derivatives; alkylsulfonic acid and / or salt thereof, dialkyl sulfosuccinate and / or salt thereof, N-acyl taurine and / or salt thereof, N-acyl-N-methyl taurine and / or salt thereof. (D) phosphoric acid derivatives; (mono and / or di) alkyl phosphoric acid and / or salt thereof, (mono and / or di) polyoxyethylene alkyl ether phosphoric acid and / or salt thereof: alkali metal ion, ammonium ion ( (Including triethanolamine salts and the like).

Examples of the nonionic surfactant, the cationic surfactant, the zwitterionic surfactant or the polymer type dispersant are as follows.
Sorbitan fatty acid esters such as sorbitan monostearate, sorbitan monolaurate and polyoxymethylene sorbitan monooleate, anionic surfactants such as sodium polyoxyethylene dodecyl ether sulfate sodium salt and sodium dodecyl ether sulfate ester, alkyl glucoside, etc. Glycoside compounds, cellulose ethers such as ethyl cellulose and benzyl cellulose, cellulose esters such as cellulose acetate, cellulose butyrate and cellulose acetate butyrate, cationic and amphoteric surface activities such as trimethylstearyl ammonium chloride and carboxymethyldimethylcetylammonium Agent, maleated polybutadiene, maleated polyethylene, maleated α-olefin, styrene-dimethyl Le aminoethyl methacrylate quaternary salt and isopropyl methacrylate - can be exemplified a polymer dispersant such as dimethylaminoethyl methacrylate quaternary salt. One or more of these dispersants can be used.
The amount used is preferably 0.001 to 5 parts by weight, more preferably 0.001 to 1 part by weight, and still more preferably 0.001 to 0.5 parts by weight with respect to 100 parts by weight of the polymerizable monomer. Part.

Moreover, as a method of making the said surfactant (dispersant) exist in the case of superposition | polymerization, the method shown to following (i)-(iv) etc. can be mentioned.
(I) A method in which a surfactant (dispersing agent) is dissolved and / or dispersed in advance in a hydrophobic organic solvent inert to the polymerization (if necessary, an amphiphilic property inert to the polymerization is also used).
(Ii) A method in which a surfactant (dispersant) is previously dissolved and / or dispersed in a polymerizable monomer or an aqueous solution thereof.
(Iii) While carrying out polymerization, a surfactant (dispersant) or a dispersion or solution thereof is gradually made into a hydrophobic organic solvent inert to the polymerization (if necessary, an amphiphilic property inert to the polymerization is also used) or polymerizable. A method of adding to a monomer (or an aqueous solution thereof).
(Iv) An addition method using the methods (i) to (iii) in combination.

The anionic surfactant is sufficiently effective even in a small amount, but the amount of the anionic surfactant is preferably 0.01 to 100 parts by weight of the polymerizable monomer. The amount is 10 parts by weight, more preferably 0.01 to 2 parts by weight, and still more preferably 0.01 to 1 part by weight. When the amount used is less than 0.01 parts by weight, not only the amount as a dispersant is small and it is not possible to stably obtain polymer particles, but also the ability to prevent degradation of the produced polymer is not sufficient, Even if the amount exceeds 10 parts by weight, the use of an excess amount of the surfactant is not economically advantageous.
Although an anionic surfactant is sufficiently effective as a dispersant even if used alone, it can be used in combination with other anionic surfactants, or it can be used as a nonionic surfactant or a cation. An ionic surfactant, an amphoteric ionic surfactant or a polymeric dispersant may be used in combination. Of these, other anionic surfactants are preferably used in combination.

In the polymerization, a polymerization initiator is preferably used.
The polymerization initiator is not particularly limited. Examples of the oxidative polymerization initiator include keto peroxides such as methyl ethyl ketone peroxide and methyl isobutyl ketone peroxide; di-tert-butyl peroxide, tert-butyl cumyl peroxide. Dialkyl peroxides such as tert-butyl peracetate, tert-butyl perisobutyrate, tret-butyl pivalate, etc .; hydroperoxides such as tert-butyl hydroperoxide, cumene hydroperoxide, hydrogen peroxide Persulfates such as potassium persulfate, sodium persulfate and ammonium persulfate; perchloric acids such as potassium perchlorate and sodium perchlorate; and halogen acid salts such as potassium chlorate and potassium bromate. One or more of these can be used.

  Examples of azo polymerization initiators include 2- (carbamoylazo) -isobutyronitrile, 2,2′-azobis (N, N′-dimethyleneisobutylamidine) dihydrohalide, 2,2′-azobis (2-amidino). Propane) dihydrohalide, 2,2'-azobis [2- (2-imidazolin-2-yl) propane] dihydrohalide, 2,2'-azobis (N, N'-dimethyleneisobutylamidine), 4,4 ' -Azobis (4-cyanopentanoic acid), 4,4'-azobis-4-cyanovaleric acid, azobisisobutyronitrile, 2,2'-azobis (4-methoxy-2,4-dimethylvalero) Nitrile), (1-phenylethyl) azodiphenylmethane, dimethyl-2,2′-azobisisobutyrate, 2,2′-azobis (2-methylbutyro Tolyl), 1,1′-azobis (1-cyclohexanecarbonitrile), 2,2′-azobis (2,4,4′-trimethylpentane), 2-phenylazo-2,4-dimethyl-4-methoxyvaleronitrile 2,2′-azobis (2-methylpropane) and the like. In the above compound, the halide is preferably chloride from the economical viewpoint. One or more of these can be used.

Furthermore, the polymerization initiator includes redox polymerization initiators such as hydrogen peroxide / ferrous salt, persulfate / sulfite, cumene hydroperoxide / ferrous salt, hydrogen peroxide / L-ascorbic acid, etc. Can also be used. One or more of these can be used.
In use, an oxidative polymerization initiator, an azo polymerization initiator, and a redox polymerization initiator may be used in combination. It can be used alone or as a mixture of two or more.
Among these, potassium persulfate, sodium persulfate, 2,2′-azobis (2-amidinopropane) dihydrohalide and 2,2′-azobis [2- (2-imidazolin-2-yl) propane] dihydrohalide are included. One or more selected from the group comprising are preferable for achieving the object of the present invention.
The usage-amount of the said polymerization initiator is 0.001 to 10% normally with respect to the said polymerizable monomer, Preferably it is 0.01 to 5%. The method for adding the polymerization initiator is not particularly limited, but it is preferably added to the polymerization solvent and / or to the monomer solution.

  Polymerize the polymerizable monomer using a hydrophobic organic solvent that is inert to polymerization (if necessary, also use amphiphilic properties that are inert to polymerization) and a polymerizable monomer (water-soluble polymerizable monomer is 50% by weight or more). As the method, any of the methods described below can be used. A method in which a polymerizable monomer or an aqueous solution thereof and a hydrophobic organic solvent are mixed together and then polymerized (collective polymerization method). A method of sequentially polymerizing a polymerizable monomer or an aqueous solution thereof dropwise into a hydrophobic organic solvent (sequential polymerization method). A method (pre-dispersion method) in which a polymerizable solution or an aqueous solution thereof is mixed or dispersed in advance with a part of a hydrophobic organic solvent and polymerized while dropping into the hydrophobic organic solvent (pre-dispersion method), Combined method. The polymerization temperature is usually in the range of 20 to 150 ° C, preferably 40 to 100 ° C. If the temperature exceeds 120 ° C., the crosslinking is extremely increased, so that the water absorption ability of the polymer particles is extremely decreased. If the temperature is less than 20 ° C., the polymerization rate is extremely decreased, which is not preferable. 0-100 degreeC is preferable and, as for the temperature of a monomer or aqueous solution, 10-40 degreeC is more preferable.

  The water-absorbing polymer in the present invention is most preferably a poly (meth) acrylic acid (salt) -based crosslinked polymer. Preferably, it has a crosslinked structure obtained by polymerizing a monomer containing (meth) acrylic acid and / or a salt thereof, preferably 50 to 100 mol%, more preferably 70 to 100 mol%, still more preferably 90 to 100 mol%. It is a polymer. The acid group in the polymer is preferably neutralized in an amount of 25 to 100 mol%, more preferably 50 to 99 mol%, and more preferably 55 to 80 mol%. More preferably, examples of the salt include one or more of alkali metal salts such as sodium, potassium and lithium, ammonium salts and amine salts. The neutralization of the acid group for forming the salt may be performed in the monomer state before polymerization, or may be performed in the polymer state during or after the polymerization, or may be used in combination. Also good.

After polymerization, if necessary, normal post-treatment, for example, azeotropic dehydration, solvent removal by decantation or centrifugation, drying using a means such as a vacuum dryer, fluid dryer, granulation treatment, granulation treatment For example, it can be obtained as polymer particles.
A conventionally known gel crushing and / or pulverizing apparatus can be used as means for making the hydrogel polymer into particles in the gel crushing step. Examples thereof include a screw type extruder having a perforated plate such as a meat chopper, an extruder, a shredder, an edge runner, a cutter mill, a screw type crusher, and the like. Further, the hydrogel polymer may be formed into particles by a shearing force generated by the rotation of the rotating arm or the stirring blade in the polymerization reaction vessel having the rotating arm or the stirring. A reaction vessel having a large stirring force for the hydrogel polymer is preferred. For example, a batch type such as a kneader, an internal mixer, a Banbury mixer, or a continuous type such as a continuous kneader can be used.

  As a method for introducing a crosslinked structure into the particles used in the present invention, a method of introducing by a self-crosslinking without using a crosslinking agent, two or more polymerizable unsaturated groups and / or two or more reactions in one molecule. Examples thereof include a method of introducing a crosslinking agent having a functional group by copolymerization or reaction. Only one type of crosslinking agent may be used, or two or more types may be used. Among them, it is preferable to use a compound having two or more reactive groups as a cross-linking agent from the viewpoint of water absorption characteristics of the obtained water-absorbent resin, and further, polyvalent ions that act on ionic groups in the water-absorbent resin. It is preferable to use in combination. In the crosslinking agent treatment in the present invention, a crosslinking agent can be added before polymerization, at the time of polymerization, and / or after polymerization. Crosslinking by a method of mixing with a polymerizable monomer solution in a polymerization step, a method of mixing in a reaction system in a polymerization step, a method of adding a polymer obtained by polymerization as a solid, aqueous solution or dispersion, etc. Can be added. As a result, a crosslinked structure can be constructed inside the particle or on the particle surface.

  Examples of the crosslinking agent include N, N-diallylacrylamide, diallylamine, triallylamine, diallylmethacrylamide, diallyl phthalate, diallyl malate, diallyl terephthalate, triallyl cyanurate, triallyl isocyanurate, triallyl. Polyallyl compounds such as phosphate, tetraallyloxyethane, pentaerythritol triallyl ether poly (meth) allyloxyalkane, divinylbenzene, N, N'-methylenebis (meth) acrylamide, (poly) ethylene glycol di (meth) acrylate, (Poly) propylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane di (meth) acrylate, glycerol tri (meth) ) Polyvinyl compounds such as acrylate, glyceryl acrylate methacrylate, ethylene oxide modified trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate; ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl Polyglycidyl ethers such as ether, glycerol diglycidyl ether, polyglycerin polyglycidyl ether; haloepoxy compounds such as epichlorohydrin, epibromhydrin, α-methylepichlorohydrin; polyaldehydes such as glutaraldehyde, glioxal; Polyols such as glycerin, polyvinyl alcohol, polyether-modified silicone; ethylenediamine, Polyamines such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyethyleneimine, polyvinylpyrrolidone, amino-modified silicone; glycidyl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, glycidyl ( Hydroxy vinyl compounds such as (meth) acrylate; polyvalent isocyanate compounds such as 2,4-tolylene diisocyanate and hexamethylene diisocyanate; polyvalent oxazoline compounds such as 1,2-ethylenebisoxazoline; urea, thiourea, guanidine, dicyandiamide, Carbonic acid derivatives such as 2-oxazolidinone, 1,3-dioxolan-2-one, 4-methyl-1,3-dioxolan-2-one, 4,5-di Tyl-1,3-dioxolan-2-one, 4,4-dimethyl-1,3-dioxolan-2-one, 4-ethyl-1,3-dioxolan-2-one, 4-hydroxymethyl-1,3 -Dioxolan-2-one, 1,3-dioxan-2-one, 4-methyl-1,3-dioxan-2-one, 4,6-dimethyl-1,3-dioxan-2-one, 1,3 -Alkylene carbonate compounds such as dioxopan-2-one, polyvalent metal compounds composed of cations such as calcium, magnesium, zinc, aluminum, iron, zirconium, titanium (inorganic or organic metal salts such as hydroxides or chlorides) ). Ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, 1,3-propanediol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, polypropylene glycol, glycerin, Polyglycerol, 2-butene-1,4-diol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1 , 2-cyclohexanol, trimethylolpropane, diethanolamine, triethanolamine, polyoxypropylene, oxyethylene-oxypropylene block copolymer, pentaerythritol, sorbitol, etc. May be used alcohol compounds, these can be used alone or in admixture.

  In the production of the water-absorbing polymer (1), the polymer particles obtained by using a polymer compound having a functional group can be subjected to a surface treatment. Examples of the polymer compound include polyethyleneimine. , Polyvinyl alcohol, polyallylamine and the like. Moreover, although this high molecular compound may be used independently, you may use together with said various crosslinking agent. The amount of the crosslinking agent having two or more polymerizable unsaturated groups or the crosslinking agent having two or more reactive groups may be any amount according to the desired performance of the water-absorbing polymer of the final product. However, it is preferably 0.001 to 20 wt%, more preferably 0.01 to 1 wt%, based on the total polymerizable monomer (polymerizable monomer other than the crosslinking agent having two or more polymerizable unsaturated groups). . When using a crosslinking agent or an aqueous solution thereof, a hydrophilic organic solvent, an acid or a pH buffering agent may be mixed and used.

  In such a treatment with a crosslinking agent, if the degree of crosslinking is increased and the interval between the crosslinking points generated on the molecular chain is increased, the amount of absorption of the water-absorbing polymer increases under pressure, and if it is shortened, the hardness of the water-absorbing polymer decreases. As a result, the flow rate under pressure decreases. In order to obtain a water-absorbing polymer having the above-described ranges of the liquid passing speed under pressure at 2.0 kPa and the water absorption amount under pressure at 2.0 kPa, the cross-linked degree was changed to produce a cross-linked polymer, Choose a well-balanced one.

For surface cross-linking, the polymer after the treatment with the cross-linking agent described above is adjusted to a specific moisture content (for example, 10 to 100% as the amount of water absorption relative to its own weight), and then the cross-linking agent as shown above is used. Then, it is carried out by causing a crosslinking reaction. By adjusting the moisture content, it is possible to control how much crosslinking penetrates into the interior. When the moisture content is increased, the reaction efficiency due to the crosslinking agent tends to decrease, but the degree of crosslinking can be further increased to the inside. In this case, it is possible to obtain a water-absorbing polymer having a high initial water-absorbing rate and which is not easily crushed under pressure. On the other hand, when the moisture content is lowered, cross-linking on the surface is likely to occur, so that a water-absorbing polymer having a high water absorption ratio can be obtained.
In the surface cross-linking, when the degree of cross-linking is increased and the interval between cross-linking points is narrowed, the amount of absorption is increased while the liquid passing speed is decreased. On the contrary, if the interval is widened, the liquid passing speed is decreased, while the absorption amount is increased. In order to obtain a water-absorbing polymer having the above-described ranges of the liquid passing speed under pressure at 2.0 kPa and the water absorption amount under pressure at 2.0 kPa, the degree of crosslinking is changed by changing the degree of crosslinking of surface crosslinking. Produce a water-absorbing polymer and select a well-balanced one.

  In the production of the water-absorbing polymer (1), the polymerization can be carried out in the presence of various additives in the polymerizable monomer as long as the polymerization is not adversely affected. Specific examples of such additives include starch-cellulose, starch-cellulose derivatives, polyvinyl alcohol, polyacrylic acid (salt), cross-linked polyacrylic acid (salt), polyethylene glycol, polyvinylpyrrolidone, and the like. Polymerization inhibitors such as auxiliaries and quinones, chain transfer agents, chelating agents and the like.

A water-absorbing polymer in which the above-mentioned two characteristics (the liquid flow rate under pressure at 2.0 kPa and the water absorption amount under pressure at 2.0 kPa) are in the above-described ranges is easier to realize when the bulk specific gravity is high. . For example, the water-absorbing polymer preferably has a bulk specific gravity of 0.5 to 0.8 g / cm ³ , more preferably 0.55 to 0.7. The form of each water-absorbing polymer is preferably a shape having a plurality of irregularities irregularly.

(Measurement method of bulk specific gravity)
The measurement was performed according to JIS K6219-2 2005.
The water-absorbing polymer was poured into the center of a cylindrical container having a known volume (a stainless steel container having a diameter of 100 mm, a capacity of 1000 ml) from a height of 50 mm or less from the edge. A sufficient amount was poured to form a triangular pyramid on the edge of the cylindrical container. Using a spatula, the sample was wiped off at the edge of the container, the weight of the sample was measured together with the container, the weight of the powder was determined, and the bulk density was calculated by dividing by the volume of the container.

The absorbent polymer (2) will be described.
The polyamino acid used in the present invention is preferably a crosslinked polyamino acid partially crosslinked. A water-absorbing polymer formed from a crosslinked polyamino acid is superior in terms of water absorption, retention, and urine stability compared to a water-absorbing polymer formed from a non-crosslinked polyamino acid. The main chain of the crosslinked polyamino acid consists of a polypeptide obtained by dehydration condensation of amino acids. When the crosslinked polyamino acid is a copolymer, the polymerization mode may be a block copolymer, a random copolymer, or a graft copolymer.

  Examples of the amino acid constituting the polyamino acid used in the present invention include alanine, valine, leucine, isoleucine, methionine, tryptophan, phenylalanine, proline, glycine, serine, threonine, cysteine, tyrosine, asparagine, glutamine, lysine, histidine, Arginine, aspartic acid, glutamic acid, etc. are mentioned. The amino acid may be an optically active substance (L form, D form) or a racemic form.

  When the polyamino acid is a copolymer of an amino acid and another monomer component other than an amino acid, examples of the other monomer component include aminocarboxylic acid, aminosulfonic acid, aminophosphonic acid, and hydroxycarboxylic acid. Examples include acid, mercaptocarboxylic acid, mercaptosulfonic acid, mercaptophosphonic acid and the like. Also, polyvalent amine, polyhydric alcohol, polyvalent thiol, polyvalent carboxylic acid, polyvalent sulfonic acid, polyvalent phosphonic acid, polyvalent hydrazine compound, polyvalent carbamoyl compound, polyvalent sulfonamide compound, polyvalent phosphonamide compound Polyvalent epoxy compounds, polyvalent isocyanate compounds, polyvalent isothiocyanate compounds, polyvalent aziridine compounds, polyvalent carbamate compounds, polyvalent carbamic acid compounds, polyvalent oxazoline compounds, polyvalent reactive unsaturated bond compounds, etc. Can be mentioned.

  The side chain group of the polyamino acid used in the present invention may be a group in an amino acid residue as it is or a group (pendant group) converted to another group. The pendant group in this case is a group bonded to the polyamino acid main chain via an amide bond, an ester bond, a thioester bond, or the like. For example, in the case of polyglutamic acid, examples of the side chain group include a carboxyl group in an amino acid residue, and examples of the pendant group include a hydrocarbon group having a carboxyl group and a hydrocarbon group having a sulfonic acid group. Moreover, the bonding position of the side chain group is not particularly limited. For example, in the case of polyaspartic acid, the carboxyl group which is a side chain group may be bonded at the α-position or at the β-position in the amino acid residue. In the case of polyglutamic acid, the carboxyl group which is a side chain group may be bonded at the α-position or the γ-position in the amino acid residue.

  The cross-linked structure in the cross-linked polyamino acid, which is a preferred polyamino acid used in the present invention, is not particularly limited. For example, a structure in which a carboxyl group in the amino acid residue of the cross-linked polyamino acid reacts or associates, or a pendant group Examples thereof include a structure in which a polar group having a crosslinking agent reacts or associates, and a self-crosslinked body in which polyamino acid main chains are directly bonded to each other.

  About the polyamino acid used for this invention, the thing by various manufacturing methods is used. Examples thereof include a culture method using a microorganism, a chemical synthesis method, and the like. Moreover, the manufacturing method of bridge | crosslinking polyamino acid is not specifically limited, either. For example, a method of cross-linking acidic amino acids to obtain a hydrogel (US Pat. No. 3,948,863; Japanese Examined Patent Publication No. 52-41309, JP-A-5-279416), a method of irradiating polyglutamic acid with γ rays (Polymer Papers, 50 Vol. 10, p. 755 (1993), Patent 203493, Patent 3416774, Patent 3715414, JP 2005-314489), Cross-linking of polyglutamic acid with a cross-linking agent (JP-A-11-343339, JP-A-2003- 192794, JP-A-2005-179534, JP-A-2001-181387, polyaspartic acid, a method of reacting aspartic acid with a crosslinking agent by heat (Japanese Patent Publication No. 6-506244; US Pat. Nos. 5,247,068 and 5,284,936). No. 7, JP-A-7-309943, JP-A-8-59820 ), And the like can be used. From the viewpoint of water absorption performance, polyaspartic acid or polyglutamic acid is preferable.

  The crosslinking agent, surface crosslinking, surface treatment and the like are the same as in the water-absorbing polymer (1). As the reaction solvent, water can be used.

The water-absorbing polymer (composite) (3) will be described.
In order to combine the particles with the water-absorbing polymer, for example, the water-absorbing polymer before or after the surface crosslinking is treated with a surface treatment agent described later.

In the present invention, the surface treatment may be performed before, at the same time, or after crosslinking, which will be described later. However, in order to further exert the effects of the present invention, the surface treatment is preferably after crosslinking. The surface treatment agent is preferably used in a proportion of 0.001 to 10% by weight, and more preferably in a proportion of 0.01 to 5% by weight with respect to the water-absorbent resin particles. The method for adding the surface treatment agent is not particularly limited, and may be dry blending or may be treated as an aqueous solution or dispersion.
The particles used for the surface treatment include aluminum sulfate, potassium alum, ammonium alum, sodium alum, (poly) aluminum chloride, polyvalent metal compounds such as hydrates thereof; polycations such as polyethyleneimine, polyvinylamine, and polyallylamine Compounds; inorganic fine particles such as silica, alumina, titanium oxide, zinc oxide, bentonite, zeolite, sepiolite, and cancrinite; and organic particles such as activated carbon can be used. These can be used individually by 1 type or in combination of 2 or more types. These may be used as aggregates or may be used in combination with another carrier.
Two or more kinds of particles used for the surface treatment can be used in combination. The average particle diameter of the porous particles such as activated carbon and silica gel is preferably 20 to 300 μm, particularly 50 to 150 μm. The average diameter of the aggregate or the complex with the carrier is preferably 150 to 600 μm, particularly preferably 200 to 500 μm. The function of these components is to suppress the smell of excreta absorbed by the absorber and the smell derived from the material.

The particles used for the surface treatment are preferably particles having a particle size distribution with different particle sizes.
Here, the particle | grains which have a particle size distribution from which a particle size differs mutually are particle | grains which satisfy | fill the following conditions. As a basic idea, it is necessary to combine particles whose bulk specific gravity after mixing is higher than that of particles alone, that is, particles that are difficult to be packed and have poor packing properties.
(A) The particle size distribution after mixing becomes wider than the particle size distribution before mixing.
(B) Mix particles having different median diameters.
Such particles are pre-classified, mixed or deleted in a specific range to obtain a desired particle size distribution, or granulated, or further granulated as necessary. Can be obtained by classification, mixing, or deletion.
By combining the particles, particularly such particles, the liquid passing speed under pressure and the water absorption amount under pressure can be easily within the above ranges.

The absorber in the first embodiment will be further described.
As the fibrous material used in combination with the water-absorbing polymer 10 as a constituent component of the fiber mixture 33, those normally used in the technical field can be appropriately used. As the fiber mixture 33, for example, a fibrous material and a water-absorbing polymer are uniformly mixed in air and molded into a specific shape, or a water-absorbing polymer is sprayed on a web to form a mixed state, or a long Examples include those obtained by spreading fibers and spraying and mixing a water-absorbing polymer, and those obtained by laminating.
Examples of the fibrous material include natural fibers such as wood pulp, plant pulp, cotton, wool, and hemp, chemically treated pulp such as crosslinked pulp and mercerized pulp, regenerated fiber such as rayon and acetate, and fiber surface with a surfactant. May be used alone or in combination such as polypropylene, polyethylene, polyethylene terephthalate, etc., and one of these may be used alone, or two or more may be used in combination. As the fibrous material, it is possible to use a cross-sectional fiber having a circular or Y-shaped, C-shaped or hollow cross section.

  The absorbent body in the first embodiment includes an absorbent layer composed of a fiber mixture 33 of the water-absorbing polymer 10 and a fibrous material, and the fiber mixture 33 has a liquid passing rate under pressure of 2.0 kPa. When it is 35 ml / min or more, particularly 50 to 120 ml / min, the liquid permeability is increased and the liquid is quickly transmitted to the lower layer absorber, or the liquid permeability in the absorber is too high. The above range is preferable because the absorption of the water-absorbing polymer does not catch up and may leak from the end. The fibrous material constituting the fiber mixture 33 is preferably a cellulose-based hydrophilic fiber such as pulp fiber, rayon, or acetate.

(Measurement method of liquid flow rate under pressure at 2.0 kPa of fiber mixture)
The measurement is performed with reference to the above-described method for measuring the liquid flow rate under pressure of the water-absorbing polymer (see paragraph [0018]).
That is, at the lower end of a vertically standing cylinder (inner diameter 25.4 mm), a wire mesh (mesh opening 150 μm, biocolumn sintered stainless steel filter 30SUS sold by Sansho Co., Ltd.) and a narrow tube with a cock (inner diameter 2 mm) ( A filtration cylindrical tube having an inner diameter of 4 mm and a length of 8 cm) was prepared.
The absorber was cut out to a diameter of 25 mm, and the absorber was set on a stainless steel filter with the cock closed. Next, a cylindrical rod having a diameter of 2 mm having a mesh with an opening of 150 μm and a diameter of 25 mm was inserted into the filtration cylindrical tube so that the mesh was in contact with the measurement sample.
Thereafter, the cock is released, and a sufficient amount of physiological saline (0.9% by weight sodium chloride solution) for swelling the absorbent as a measurement sample, for example, physiological saline more than 5 times the saturated absorption of the water absorbent. Soak for 30 minutes.
Next, the entire filtration cylindrical tube is taken out from the physiological saline, and a weight is placed so that a load of 2.0 kPa is applied to the measurement sample. The cock is closed, the filtering cylindrical tube is filled with physiological saline, and left for 1 minute, and then the cock is opened to flow the liquid, and the time (T ₁ ) (seconds) through which 20 mL of liquid passes is measured. Using the measured time T ₁ (seconds), the flow rate at 2.0 kPa is calculated from the following equation. In the formula, T ₀ (seconds) is a value obtained by measuring the time required for 20 ml of physiological saline to pass through the wire mesh without putting the measurement sample in the filtering cylindrical tube.
Flow rate (ml / min) = 20 × 60 / (T ₁ −T ₀ )
The value obtained by the above formula is divided by the thickness of the swollen water-absorbing polymer layer in the cylinder, and converted to a value per 20 mm to obtain a liquid passing speed under pressure. The measurement was performed 5 times (n = 5), the values at each of the upper and lower points were deleted, and the average value of the remaining three points was taken as the measured value.
In the absorber, when the area of the region to be measured is small and sampling of the above size cannot be performed, a plurality of regions are collected to adjust the sample. The measured value shall include an operational error at this time.

In the first embodiment, the mixing ratio (content ratio) of the water-absorbing polymer 10 and the fibrous material in the fiber mixture 33 is a weight ratio when fibers having a length of less than 5 mm are used as the fibrous material. Water-absorbing polymer / fibrous material) = 1/1 to 3/1 is preferable, and 1.5 / 1 to 2.5 / 1 is more preferable. When the fibrous material is a fiber having a length exceeding 10 mm, further exceeding 30 mm, further exceeding 70 mm, or using a continuous fiber, (by weight ratio) (water absorbent polymer / fibrous material) = 1/1 to 15 / 1 is preferable and 3/1 to 10/1 is more preferable.
Such a mixing ratio is preferable in that extreme movement of the water-absorbing polymer does not occur and absorption of the liquid and efficient use of the absorber and the water-absorbing polymer.
Normally, the content weight ratio of the water-absorbing polymer to the fibrous material in this type of absorbent body (fiber mixture) is (water-absorbing polymer / fibrous material) = 1 or less, and the content weight ratio is 1 The above absorbent body is an absorbent body having a so-called pulpress structure in which the ratio of the fibrous material is small. Such a pulpress structure can reduce the bulk by reducing the amount of the fibrous material used, so that the absorber can be thinned and is effective in improving the feeling of wearing the absorbent article. Moreover, in 1st Embodiment, the usage-amount of a fibrous material can be reduced and the absorber of a thin pal press structure can be used by using the water absorbing polymer 10 excellent in the various characteristics mentioned above.
In order to mix the short fibers and the water-absorbing polymer at a reduced ratio of the fibrous material, a device for disturbing the air flow in the duct (for example, a triangular plate is arranged in the duct and the air flows partially with respect to the air flow. The speed of the gas is changed by narrowing the path, and high-pressure air can be used in combination with the introduction of the water-absorbing polymer. )) Is necessary.

The absorbent body 3 according to the first embodiment is a fiber having an upper absorbent layer 31 composed of a fiber mixture 33 of the water-absorbing polymer 10 and a fibrous material. In the case of using a continuous fiber exceeding 70 mm, it is preferable to further have a lower absorbent layer 32 disposed on the non-skin contact surface side of the absorbent layer 31. With such a structure, spot absorptivity can be imparted by quick absorption by the upper absorbent layer. As a result, the area that wets the skin is reduced, and skin troubles can be reduced. On the other hand, it is preferable to impart diffusibility to the lower absorption layer because an absorption capacity and quick absorption can be realized.
In addition, by causing a difference in absorption rate between the upper absorbent layer 31 and the lower absorbent layer 32, liquid diffusion occurs near the interface between the upper and lower absorbent layers, thereby suppressing local swelling of the absorbent body, and wearing discomfort. Can be reduced and the pressure applied to the body can be dispersed.
As the fibrous material contained in the lower absorbent layer 32, the same fibrous material in the upper absorbent layer 31 can be used.
The lower absorbent layer 32 may not include the water absorbent polymers 10 and 11.

Hereinafter, the diaper 1 of 1st Embodiment is further demonstrated.
The diaper 1 has an hourglass-like shape with a central portion in the longitudinal direction corresponding to the crotch portion as a whole. The top sheet 2 and the back sheet 4 respectively extend outward from the left and right side edges and the front and rear ends of the absorber 3. The top sheet 2 has a width direction S smaller than the back sheet 4 in the width direction. The diaper 1 is an unfolded diaper, and a pair of fastening tapes FT are attached to both side edges at one end in the longitudinal direction L. Further, a landing tape LT is attached on the back sheet 4 at the other end.

The diaper 1 includes a three-dimensional gather that can rise above the widthwise side edge of the absorber 3. That is, on each side of the diaper 1 in the longitudinal direction L, a sheet material 60 for forming a three-dimensional gather having the elastic member 6 is disposed to form a three-dimensional gather.
In addition, on one side of the diaper 1 in the longitudinal direction L, a pair of left and right or one (two in the first embodiment) elastic members 7 and 7 for forming leg gathers are arranged, and the leg gathers are arranged. Is formed. The elastic members 7 for forming leg gathers are arranged in a substantially linear shape in an extended state in the leg flaps extending outward from both longitudinal side edges of the absorber 3.

  One or a plurality of the elastic members 6 (three in the first embodiment) are fixed to one side edge of the sheet material 60 for forming a three-dimensional gather. The sheet material 60 is joined to the surface sheet 2 along the longitudinal direction L of the diaper 1 at positions outside the left and right side edges of the absorbent body 3 in the width direction S. The rising base end portion 61 of FIG. The sheet material 60 extends outward from the rising base end portion 61 in the width direction S of the diaper 1, and is joined to the back sheet 4 at the extended portion. The sheet material 60 is bonded onto the top sheet 2 at the front and rear end portions 62 and 63 in the diaper longitudinal direction L.

  As the surface sheet 2, various types conventionally used in this type of diaper can be used, and there is no limitation as long as it can permeate liquid such as urine. For example, synthetic fiber or natural fiber And woven fabrics, nonwoven fabrics, and porous sheets. As the back sheet 4, various types conventionally used in this type of diaper can be used, and liquid-impermeable or water-repellent and moisture-permeable ones are preferably used.

The diaper 1 of 1st Embodiment can be used similarly to a normal expansion | deployment type diaper. This diaper 1 has a high water absorption rate for body fluids such as urine and is excellent in liquid permeability due to the action of the water-absorbing polymer 10 contained in the absorbent body 3. It can absorb quickly (spot absorption) without spreading unnecessarily in the direction, does not easily cause wetback or gel blocking, and hardly causes stickiness or liquid leakage.
Further, the water-absorbing polymer 10 has a liquid absorption amount under pressure at 2.0 kPa of less than the predetermined value, and even when liquid is absorbed, the thickness of the portion does not increase greatly. Therefore, even when the water-absorbing polymer absorbs the liquid when the absorbent article is worn, it can prevent the wearer from feeling uncomfortable and can also prevent the pressure sore from being induced. .

FIG. 3 is a view showing a sanitary napkin 1A according to the second embodiment of the present invention. A sanitary napkin 1A according to the second embodiment includes a liquid-permeable top sheet 2, a liquid-impermeable (including poorly-permeable) back sheet 4, and an absorbent body 3 interposed between the two sheets 2 and 4. It has.
The absorbent body 3 in the second embodiment is the same as the absorbent body 3 in the disposable diaper 1 of the first embodiment. The above-described two characteristics (pressurization rate under pressure at 2.0 kPa, under pressure at 2.0 kPa) The water-absorbing polymer 10 satisfying the (water absorption amount) is included.

  As shown in FIG. 3, the absorbent body 3 in the second embodiment includes a lower layer 36 and an upper layer 35 having liquid permeability, and the upper layer 35 and the lower layer 36 sandwich the water-absorbing polymer 10. The absorber 3 is formed by spraying a large number of water-absorbing polymers 10 between the upper layer 35 and the lower layer 36. The absorber 3 (the lower layer 36) and the back sheet 4 are joined by a known joining means such as a hot melt adhesive. A large number of water-absorbing polymers 10 are adhered to each other and / or to the upper layer 35 and the lower layer 36 by expressing the adhesiveness of the polymers themselves. It does not contain a binder for attaching the polymers 10 to each other or to the upper layer 35 or the lower layer 36.

  The water-absorbing polymer 10 is usually sprayed between the upper layer 35 and the lower layer 36 by spraying water on the upper layer 35 or the lower layer 36 or the water-absorbing polymer 10 itself, or by the moisture absorption of the water-absorbing polymer itself. If the water-absorbing polymer 10 has a moisture content of more than 10%, preferably more than 15%, the water-absorbing polymer 10 has high hygroscopicity, and the upper layer 35 and the lower layer 36 It is possible to absorb the moisture in the air after being sprayed between the two and express adhesiveness, so that it is not necessary to spray water.

As described above, the upper layer 35 sandwiching the water-absorbing polymer 10 has liquid permeability. The upper layer 35 can be made of a material having liquid permeability. Examples of the liquid permeable material include nonwoven fabric, paper, perforated film, fluff pulp and the like. Among these, nonwoven fabric, paper, and fluff pulp are particularly preferable from the viewpoint of liquid permeability and water absorption. Non-woven fabrics such as air-through nonwoven fabric, thermal bond nonwoven fabric, spunbond nonwoven fabric, spunbond-meltblown-spunbond (SMS) nonwoven fabric, spunbond-meltblown-meltblown-spunbond (SMMS) nonwoven fabric, etc. Or airlaid nonwoven fabric, spunlace nonwoven fabric, and the like.
Here, the liquid does not necessarily pass through the lower layer 36 to the back sheet side in the thickness direction, and the liquid permeability is imparted only in the skin contact surface side portion (upper layer portion) and the lower layer of the lower layer 36. be able to.
That is, the lower layer 36 can be made from a plurality of materials, and a leak-proof layer can be provided on the back material side. Examples of the leak-proof layer include various nonwoven fabrics (not hydrophilized) such as spunbond nonwoven fabric, spunbond-meltblown-spunbond (SMS) nonwoven fabric, and spunbond-meltblown-meltblown-spunbond (SMMS) nonwoven fabric. Used. In this case, the fibers used for the lower layer nonwoven fabric are preferably fibers that are thinner than the fibers used for the upper layer (fibers of less than 2 dtex, more preferably fibers of less than 1 dtex) and split fibers, from the viewpoint of improving leakage resistance.

When the upper layer 35 is made of a nonwoven fabric, the basis weight of the upper layer 35 is preferably 5 to 50 g / m ² , more preferably 10 to 40 g / m ² , and the thickness is preferably 0.1 to 5 mm, more preferably. Is 0.1 to 3 mm. When the upper layer 35 is made of fluff pulp, the basis weight of the upper layer 35 is preferably 10 to 300 g / m ² , more preferably 30 to 200 g / m ² , and the thickness is preferably 0.5 to 5 mm, Preferably it is 1-3 mm. When the upper layer 35 is made of paper, the basis weight of the upper layer 35 is preferably 5 to 40 g / m ² , more preferably 10 to 35 g / m ² , and the thickness is preferably 0.1 to 3 mm, more preferably. Is 0.1-1 mm.

When the lower layer 36 is made of a nonwoven fabric, the basis weight of the lower layer 36 is preferably 5 to 50 g / m ² , more preferably 20 to 40 g / m ² , and the thickness is preferably 0.1 to 5 mm, more preferably 0.1 to 3 mm. When the lower layer 36 is made of fluff pulp, the basis weight of the lower layer 36 is preferably 10 to 500 g / m ² , more preferably 30 to 300 g / m ² , and the thickness is preferably 0.5 to 5 mm, more preferably Is 1 to 3 mm. When the lower layer 36 is made of paper, the basis weight of the lower layer 36 is preferably 5 to 30 g / m ² , more preferably 5 to 20 g / m ² , and the thickness is preferably 0.1 to 3 mm, more preferably. Is 0.1-1 mm.

  In addition to the water-absorbing polymer 10, pulp fibers can be included between the upper layer 35 and the lower layer 36. The weight ratio of pulp / water-absorbing polymer can be, for example, 50/50 to 0/100.

  As the water-absorbing polymer 10 in the absorbent body according to the second embodiment, the above-mentioned two characteristics (pressure passing liquid under pressure at 2.0 kPa, water absorption under pressure at 2.0 kPa) are in the above-mentioned ranges, respectively. By using a polymer, a highly viscous liquid can be quickly absorbed and diffused in the absorber.

4 and 5 are views showing a sanitary napkin 1B according to a third embodiment of the present invention. The absorbent body 3 in the sanitary napkin 1B of the third embodiment is the same as the absorbent body 3 in the disposable diaper 1 of the first embodiment. An upper absorbent layer 31 composed of a fiber mixture 33 of a water-absorbing polymer and a fibrous material satisfying (water absorption under pressure at 0 kPa), and a second water-absorbing polymer that may or may not satisfy the two characteristics. The lower absorption layer 32 which consists of the fiber mixture 34 with a fibrous material is comprised.
The upper absorbent layer 31 in the sanitary napkin 1B is smaller than the lower absorbent layer 32, and is disposed in a part that is disposed opposite to the liquid excretion part of the wearer at the time of wearing. The middle-high part A which protrudes toward the skin side is formed.
The upper absorbent layer 31 according to the third embodiment also includes a water-absorbing polymer that satisfies the above-described two characteristics (the liquid flow rate under pressure at 2.0 kPa and the amount of water absorbed under pressure at 2.0 kPa). Even if A absorbs the liquid, the portion does not protrude more than necessary, so that the uncomfortable feeling can be prevented.
The point which is not demonstrated especially regarding the absorber 3 of the sanitary napkin 1B is the same as that of 2nd Embodiment.

As mentioned above, although this invention was demonstrated based on the preferable embodiment, this invention is not restrict | limited to the said embodiment.
For example, the absorbent article of the present invention may be a pants-type disposable diaper, a panty liner, an incontinence liner, an absorbent pad (urine collecting pad), etc., in addition to a deployable disposable diaper and a sanitary napkin. Further, the back sheet may be impermeable to moisture. The absorbent article of the present invention is mainly used for absorbing and holding excretory body fluids such as urine and menstrual blood.

  Further, in the absorbent body 3 in the first and second embodiments, the fiber aggregate 33 constituting the upper absorbent layer 31 and the fiber aggregate 34 constituting the lower absorbent layer 32 may not be covered with a covering sheet, respectively. Moreover, both may be collectively wrapped with one or a plurality of covering sheets.

Moreover, although the absorber 3 in 1st Embodiment had the structure where the whole area | region laminated | stacked the upper absorption layer 31 and the lower absorption layer 32, only one part has such a two-layer structure. For example, only the part disposed opposite to the urine excretion part indicated by P in FIG. 1, or only the both sides in the longitudinal direction of the absorber 3 and the front and rear end parts in the longitudinal direction, It may have a two-layer structure. Moreover, the water absorption which satisfy | fills the above-mentioned two characteristics (the liquid flow rate under pressure in 2.0 kPa, the water absorption amount under pressure in 2.0 kPa) in the whole or only part of the absorber of the single layer structure of an absorbent article. Polymers can also be placed.
In addition, the description omitted in one embodiment and the requirements of only one embodiment can be applied to other embodiments as appropriate, and the requirements in each embodiment can be appropriately applied between the embodiments. Can be substituted for each other.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited to these.

[Synthesis Example 1]
A SUS304 5L reaction vessel (using anchor blades) that can be attached with a stirrer, reflux condenser, monomer dropping port and nitrogen gas inlet tube to maintain a good airtight state. 3. (Alkyl group: C12 / C78 = 72/28, EO average added mole number: 1 mole of AES) 0.2% [weight of acrylic acid as an active ingredient] and ethylenediaminetetraacetic acid trisodium dihydrate 6 mg was charged and 1600 mL of normal heptane was added. While controlling the pressure in the container to a predetermined pressure (around 70 kPa), nitrogen gas was blown in and the bath temperature was raised to 80 ° C. while stirring. The reflux state was maintained for 30 minutes.
Meanwhile, in a 2 L three-necked flask, 500 g of 80% acrylic acid manufactured by Toagosei Co., Ltd. and 250 g of ion exchange water were charged, and 350 g of 48% sodium hydroxide aqueous solution manufactured by Asahi Glass was added dropwise while cooling with ice, and 1100 g of sodium acrylate aqueous solution as a monomer aqueous solution. Got. To this aqueous monomer solution, 0.2 g of N-acylated sodium glutamate (trade name: Amisoft GS-11F) manufactured by Ajinomoto Co., Inc. was added to 3 g of ion-exchanged water, and after stirring for a while, 350 g, 200 g, and 550 g were added. Divided into three parts.
Subsequently, 0.2 g of 2,2′-azobis (2-amidinopropane) dihydrochloride (trade name V-50) manufactured by Wako Pure Chemical Industries, Ltd., ISP TECHNOLOGIES, INC. Polyvinylpyrrolidone (K-15) (0.2 g) and ion-exchanged water (14 g) were mixed and dissolved to prepare an initiator (A) aqueous solution. Moreover, 0.6 g of sodium persulfate manufactured by Wako Pure Chemical Industries, Ltd. was dissolved in 12 g of ion-exchanged water to prepare an initiator (B) aqueous solution. Furthermore, a titanium citrate aqueous solution (50% citric acid and 7.6% (TiO2) titanyl sulfate aqueous solution were mixed at a weight ratio of 33/439) was prepared.
10 g of initiator (A) was added to one of the three divided monomer aqueous solutions (350 g) (monomer (1)). Moreover, 5 g of initiator (A) and 1 g of titanium citrate aqueous solution were added to another monomer aqueous solution (200 g) divided into three (monomer (2)). To the remaining monomer aqueous solution (550 g) divided into three, 10 g of initiator (B) and 3.5 g of titanium citrate aqueous solution were added (monomer (3)).
After confirming that the normal heptane in the 5 L reaction vessel was sufficiently refluxed, the monomer (1) was dropped from the monomer dropping port using a microtube pump over 20 minutes for polymerization. Subsequently, the monomer (2) was added dropwise over 10 minutes for polymerization. Subsequently, the monomer (3) was added dropwise over 30 minutes for polymerization.
Five minutes after the completion of the monomer dropping, the pressure was returned to normal pressure, and azeotropic dehydration was performed using a dehydrating tube to adjust the water content of the water-absorbing polymer (hydrogel) to 65 parts by weight with respect to 100 parts by weight of the water-absorbing polymer. Then, what melt | dissolved 0.2g ethylene glycol diglycidyl ether (brand name Denacol EX-810) by Nagase Chemical Industries as a crosslinking agent in 10g of water was added. Thereafter, azeotropic dehydration was further performed to adjust the water content of the water-absorbing polymer (hydrogel) to 35 parts by weight with respect to 100 parts by weight of the water-absorbing polymer. After cooling, the solvent was removed and dried to obtain a water-absorbing polymer.
With respect to the obtained water-absorbing polymer, the water-absorbing polymer having a large particle size was removed by sieving to obtain a water-absorbing polymer having an average particle size of 390 μm. Further, 0.5 part by weight of Aerosil (average particle size μm) manufactured by Nippon Aerosil Co., Ltd. was surface-treated by dry blending with respect to 100 parts by weight of the water-absorbing polymer, and the absorbed amount under pressure was 19 g / g. A water-absorbing polymer having a speed of 105 ml / min and a bulk specific gravity of 0.70 g / cm ³ was obtained.

[Synthesis Example 2]
A SUS304 5L reaction vessel (using anchor blades) equipped with a stirrer, reflux condenser, monomer dripping port, nitrogen gas inlet tube, thermometer, Toho Chemical polyoxyethylene alkyl ether sodium sulfate (trade name Arscope) N-3T) was charged with 0.1% [weight of acrylic acid as an active ingredient], and 1600 mL of normal heptane was added. Nitrogen gas was blown for the purpose of expelling dissolved oxygen, and the temperature was raised to an internal temperature of 90 ° C. at normal pressure while stirring.
Meanwhile, in a 2 L three-necked flask, 500 g of 80% acrylic acid (act. 80.6% manufactured by Toagosei Co., Ltd.) and 220 g of ion-exchanged water were charged, and a 48% sodium hydroxide aqueous solution (act. 49.6 manufactured by Asahi Glass Co., Ltd.) was cooled with ice. %) 330 g was dropped to obtain 1030 g of a sodium acrylate aqueous solution (72% neutralized product) as an aqueous monomer solution. To this aqueous monomer solution, 0.25 g of N-acylated glutamic acid soda (trade name: Amisoft PS-11 manufactured by Ajinomoto Co., Inc.) dissolved in 3 g of ion-exchanged water was added, and then divided into 250 g, 250 g, and 530 g.
Subsequently, 2,2′-azobis (2-amidinopropane) dihydrochloride (trade name V-50 manufactured by Wako Pure Chemical Industries, Ltd.) 0.05 g, polyethylene glycol (K-PEG 6000 LA manufactured by Kao Corporation) 0.2 g, ion-exchanged water 10 g Were mixed and dissolved to prepare an initiator (A) solution. Moreover, 0.6 g of sodium persulfate (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 10 g of ion-exchanged water to prepare an initiator (B) solution. Further, a titanium citrate aqueous solution (citric acid / Ti molar ratio 1.0, solid content 19.0%, Ti amount 0.04% [to acrylic acid]) was prepared.
To one of the three divided monomer aqueous solutions (250 g), 2.5 g of the initiator (A) solution was added (monomer (1)). Further, 7.5 g of the initiator (A) solution and 1.57 g of the titanium citrate aqueous solution were added to another monomer aqueous solution (250 g) divided into three (monomer (2)). 10.5 g of initiator (B) solution and 3 g of titanium citrate aqueous solution were added to the remaining three monomer aqueous solutions (530 g) (monomer (3)).
After confirming that the internal temperature of the 5 L reaction vessel was 90 ° C., the monomer (1) that was allowed to stand for 5 minutes or more was dropped from the monomer dropping port over 15 minutes and polymerized. Subsequently, the monomer (2) was added dropwise over 15 minutes for polymerization. Subsequently, the monomer (3) was added dropwise over 30 minutes for polymerization.
After completion of the monomer dropping, azeotropic dehydration was performed using a dehydrating tube, and the water content of the water-absorbing polymer (hydrogel) was adjusted to 60 parts by weight with respect to 100 parts by weight of the water-absorbing polymer. Thereafter, 0.1 g of ethylene glycol diglycidyl ether (manufactured by Nagase Chemicals, trade name Denacol EX-810) dissolved in 10 g of water was added as a crosslinking agent. Thereafter, azeotropic dehydration was further performed to adjust the water content of the water-absorbing polymer (hydrogel) to 40 parts by weight with respect to 100 parts by weight of the water-absorbing polymer. A water-absorbing polymer was obtained by cooling and drying.
With respect to the obtained water-absorbing polymer, the water-absorbing polymer having a large particle diameter was removed by sieving to obtain a water-absorbing polymer having an average particle diameter of 370 μm. Furthermore, the surface treatment was performed on 100 parts by weight of the water-absorbing polymer in the same manner as in Synthesis Example 1, and the water absorption was 16 g / g under pressure, the liquid passing speed under pressure was 55 ml / min, and the bulk specific gravity was 0.74 g / cm ³ . A polymer was obtained.

[Synthesis Example 3]
A SUS304 5L reaction vessel (using anchor blade) equipped with a stirrer, reflux condenser, monomer dropping port, nitrogen gas inlet pipe, thermometer, polyoxyalkylene ether phosphate (stirrer, reflux condenser, A 5-L four-necked round bottom flask equipped with a thermometer and a nitrogen gas introduction tube was charged with a polyoxyalkylene (EO = 5, PO = 4, EO = 5 triblock type) alkyl (C12 / C14 = 7/3). (Weight ratio of raw alcohol)) 3000 g of ether (OHV: 63.8) was added, and nitrogen gas was introduced at 50 mL / min, stirring was performed at 200 rpm, and the temperature was raised. After reaching the value of 40 ° C. (inner temperature was 35 to 38 ° C.), nitrogen substitution was performed for 40 minutes, where 180 g of phosphoric anhydride was added so that the inner temperature did not exceed 60 ° C. During the addition, the nitrogen gas inlet tube was removed, and a powder funnel was inserted into the flask mouth.After the addition was completed, the internal temperature was raised to 60 ° C., and the mixture was stirred for 1 hour. Furthermore, the internal temperature was raised to 80 ° C., and the mixture was stirred for 15 hours, to which 95.3 g of ion-exchanged water was added, and further stirred for 4 hours.
The 5L scale synthesis reaction was performed 12 times, and a mixture of 12 lots of products was used. ) 0.1% [weight of acrylic acid, as active ingredient] was added, and 1600 mL of normal heptane was added. Nitrogen gas was blown for the purpose of expelling dissolved oxygen, and the temperature was raised to an internal temperature of 90 ° C. at normal pressure while stirring.
Meanwhile, in a 2 L three-necked flask, 500 g of 80% acrylic acid (act. 80.6% manufactured by Toagosei Co., Ltd.) and 220 g of ion-exchanged water were charged, and a 48% sodium hydroxide aqueous solution (act. 49.6 manufactured by Asahi Glass Co., Ltd.) was cooled with ice. %) 330 g was dropped to obtain 1050 g of a sodium acrylate aqueous solution (72% neutralized product) as an aqueous monomer solution. To this aqueous monomer solution, 0.25 g of N-acylated glutamic acid soda (Ajinomoto trade name Amisoft GS-11F) dissolved in 3 g of ion-exchanged water was added, and then divided into 250 g, 250 g, and 550 g.
Next, 0.02 g of 2,2′-azobis (2-amidinopropane) dihydrochloride (trade name V-50 manufactured by Wako Pure Chemical Industries), 0.2 g of polyethylene glycol (K-PEG6000 LA manufactured by Kao), 10 g of ion-exchanged water Were mixed and dissolved to prepare an initiator (A) solution. Further, 0.184 g of sodium persulfate (manufactured by Wako Pure Chemical Industries, Ltd.) 0.184 g 2,2′-azobis (2-amidinopropane) dihydrochloride (trade name V-50, manufactured by Wako Pure Chemical Industries, Ltd.) is dissolved in 10 g of ion-exchanged water. Initiator (B) solution was prepared.
To one of the three aqueous monomer solutions (250 g), 3.5 g of the initiator (A) solution was added (monomer (1)). Further, 3.5 g of the initiator (A) solution was added to another monomer aqueous solution (250 g) divided into three (monomer (2)). 10 g of the initiator (B) solution was added to the remaining monomer aqueous solution (550 g) divided into three (monomer (3)).
After confirming that the internal temperature of the 5 L reaction vessel was about 90 ° C., the monomer (1) that was allowed to stand for 5 minutes or more from the monomer dropping port was dropped over 15 minutes to polymerize. . Subsequently, the monomer (2) was added dropwise over 15 minutes for polymerization. Subsequently, the monomer (3) was added dropwise over 30 minutes for polymerization.
After completion of the monomer dropping, azeotropic dehydration was performed using a dehydrating tube, and the water content of the water-absorbing polymer (hydrogel) was adjusted to 60 parts by weight with respect to 100 parts by weight of the water-absorbing polymer. Then, what melt | dissolved 0.25 g of ethylene glycol diglycidyl ether (Nagase Kasei Kogyo make, brand name Denacol EX-810) in 10 g of water was added as a crosslinking agent. Thereafter, azeotropic dehydration was further performed to adjust the water content of the water-absorbing polymer (hydrogel) to 35 parts by weight with respect to 100 parts by weight of the water-absorbing polymer. A water-absorbing polymer was obtained by cooling and drying.
With respect to the obtained water-absorbing polymer, the water-absorbing polymer having a large particle size was removed by sieving to obtain a water-absorbing polymer having an average particle size of 390 μm. Further, the surface treatment was performed on 100 parts by weight of the water-absorbing polymer in the same manner as in Synthesis Example 1, the water absorption was 18 g / g under pressure, the liquid passing rate under pressure was 80 ml / min, and the bulk specific gravity was 0.79 g / cm ³ . A polymer was obtained.

[Comparative Synthesis Example 1]
Sodium acrylate, polyethylene glycol diacrylate and D-sorbitol used in Synthesis Example 1 were dissolved to obtain a reaction solution. Next, it was degassed for 20 minutes under a nitrogen gas atmosphere. Subsequently, a 10% aqueous solution of sodium persulfate and a 0.1% aqueous ascorbic acid solution were added dropwise with stirring. Polymerization was carried out at 20 to 95 ° C. while pulverizing the generated gel, and a hydrate was taken out 30 minutes after the start of the polymerization. The hydrogel was spread on a wire mesh, dried with an electric dryer, and pulverized using a roll mill. The obtained pulverized product was sieved to match the particle size distribution of the water-absorbing polymer of Synthesis Example 1.
The obtained water-absorbing polymer obtained a superabsorbent polymer having an average particle size of 350 μm, an absorption amount under pressure of 21 g / g, a liquid passage speed under pressure of 35 ml / min, and a bulk specific gravity of 0.43 g / cm ³ .

[Comparative Synthesis Example 2]
2,2′-azobis (2-amidinopropane) dihydrochloride as an initiator in an ion exchange aqueous solution of sodium acrylate and N-acylated glutamic acid sodium (Ajinomoto trade name Amisoft GS-11F) used in Synthesis Example 1 Wako Pure Chemical Industries, Ltd., trade name V-50) and polyethylene glycol (K-PEG 6000 LA, manufactured by Kao) were mixed and dissolved to prepare a monomer solution.
Next, in place of the dispersant of Synthesis Example 1, 0.11% of polyoxyalkylene ether sulfate [weight of acrylic acid, as active ingredient] was charged, and normal heptane was added as a solvent. Thereafter, a water-absorbing polymer was obtained in the same manner as in Synthesis Example 1.
About the obtained water-absorbing polymer, about the obtained water-absorbing polymer, the superabsorbent polymer with a large particle diameter was removed by sieving, the average particle diameter was 320 μm, the absorption amount under pressure was 12 g / g, and the liquid flow rate under pressure. A superabsorbent polymer having a volume specific gravity of 3 ml / min and a bulk specific gravity of 0.64 g / cm ³ was obtained.

  Table 1 shows the average particle size, the absorption under pressure (under 2.0 kPa), and the water absorption rate under pressure by the vortex method for each of the water-absorbing polymers obtained in Synthesis Examples 1 to 3 and Comparative Synthesis Examples 1 and 2. The speed (under 2.0 kPa) and bulk specific gravity are summarized.

[Example 1]
100 parts by weight of the defibrated pulp (fluff pulp) and 200 parts by weight of the water-absorbing polymer of Synthesis Example 1 were mixed in an air stream and piled while sucking from the inner surface of the mesh. The total basis weight of the pulp / water-absorbing polymer mixed fiber was 450 g / m ² . The resulting fiber stack was wrapped in a tissue paper having a basis weight of 16 g / m ² and spray-coated with a hot melt pressure-sensitive adhesive to obtain an absorbent body.

[Example 2]
First, a crimped acetate long fiber tow was prepared. The fiber diameter of this long fiber was 2.1 dtex. The total fiber content of tow was 25,000 dtex. This tow was conveyed under extension and opened using an air opening device to obtain an opening web. Next, the web was wound through a spread web between a roll in which a large number of disks were incorporated around the axis at predetermined intervals and a smooth receiving roll. Thereafter, the width was adjusted to 100 mm, and the transfer speed was reduced and transferred onto a vacuum conveyor. The tension of the web on the vacuum conveyor was relaxed to cause crimps. The crimp ratio of the fibers in the web was 30%, and the number of crimps per 1 cm was 15. This widened the space between the long fibers, made it easier for the absorbent polymer to enter, and increased the thickness of the web to improve the embedding supportability of the absorbent polymer. The absorbent polymer obtained in Synthesis Example 1 with a width of 80 mm was sprayed on the web, and the absorbent polymer was embedded and supported in the spread web. The basis weight of the web was 25 g / m ² and the basis weight of the absorbent polymer was 132 g / m ² .
Next, 100 parts by weight of the opened fluff pulp and 100 parts by weight of the absorbent polymer obtained in Synthesis Example 1 were uniformly mixed in an air stream and stacked on a T-shaped mold, for a total basis weight of 300 g. An accumulated fiber of / m ² was obtained. The T-shaped mold had a leg width of 100 mm, a length of 100 mm, a horizontal frame width of 125 mm, and a length of 100 mm. The basis weights of the fluff pulp and the absorbent polymer in the piled body were 150 g / m ² , respectively. The web was layered on the piled fiber, and the whole was wrapped with a tissue paper having a basis weight of 16 g / m ² spray-coated with a hot melt adhesive. Thereafter, compression is performed between a metal roll and a rubber roll (the clearance between the two rolls is set to 0 mm), and the web and tissue paper are integrated, and the web is compressed, and the constituent fibers of the web are compressed by the absorbent polymer. The absorbent body was obtained by cutting.
This web (fiber aggregate or long fiber web) contains the water-absorbing polymer and short fibers of Synthesis Example 1, and the distribution of the short fibers in the absorbent body is 80 mm in the center in the width direction (absorbing the absorbent polymer). Existed in a biased position). The existence ratio of short fibers in the central region in the web width direction was 86% (long fibers were 14%), and the existence ratio of short fibers at both ends in the web width direction was 18%.

[Examples 3 and 4]
An absorbent body was obtained in the same manner as in Example 2 except that the water-absorbing polymers of Synthesis Example 2 and Synthesis Example 3 were used instead of the water-absorbing polymer of Example 2.

Example 5
In place of the acetate continuous fiber of Example 2, an air-through nonwoven fabric (fiber thickness, 3.3 dtex, basis weight 40 g / m ² ) made of a composite eccentric fiber having a core made of polyethylene terephthalate and a sheath made of high-density polyethylene was used. An absorbent body was obtained in the same manner as in Example 2 except that the water-absorbing polymer of Synthesis Example 2 was used as the water-absorbing polymer.

Example 6
As a surface treatment agent for the water-absorbing polymer of Synthesis Example 2, Nippon Aerosil Co., Ltd. used in Synthesis Example 1, 100 parts by weight of porous silica particles (average particle size 2 μm), and Mizusawa Chemical Co., Ltd., Zeolite (Silton) (B, average particle size) 100 parts by weight of a uniform mixture was dry-blended to adhere to 5% by weight of the water-absorbing polymer. Other than that was carried out similarly to Example 2, and obtained the absorber.

Example 7
The absorber of Example 1 was changed as follows. First, 70 parts of softwood pulp (NBKP) and 30 parts of pulp having a crimp structure (trade name: HighBulk Additive (hereinafter referred to as HBA), Wafer User Co., Ltd.) are stirred and mixed in water as a water-soluble binder. Disperse 5 parts of polyvinyl alcohol (hereinafter referred to as PVA) (trade name: Gohsenol p-250, Nippon Synthetic Chemical Co., Ltd.) and 10 parts of dialdehyde starch (trade name: Caldas, Nippon Carlit Co., Ltd.) in water. These were paper-made and dried, and then a bulky paper having a weight of 25 g / m ² was obtained.
The obtained paper was adjusted to a moisture content of 100% (containing water of the same weight as the paper's own weight), sprayed with 50 g / m ² of the above water-absorbing polymer, An absorbent body in which a water-absorbing polymer was sandwiched between two bulky papers was obtained. The bulky paper and the water-absorbing polymer are fixed by the adhesiveness of the water-absorbing polymer or PVA contained in the bulky paper. The obtained absorbent body is suitable as an absorbent body for sanitary napkins.

[Comparative Example 1]
An absorbent body was obtained in the same manner as in Example 1 except that the water-absorbing polymer in Example 1 was changed to the water-absorbing polymer in Comparative Synthesis Example 1.

[Comparative Example 2]
An absorbent body was obtained in the same manner as in Example 1 except that the water-absorbing polymer in Example 1 was changed to the water-absorbing polymer in Comparative Synthesis Example 2.

[Comparative Example 3]
An absorbent body was obtained in the same manner as in Example 1 except that the water-absorbing polymer in Example 7 was changed to the water-absorbing polymer in Comparative Synthesis Example 2.

  For the absorbers obtained in Examples 1 to 6 and Comparative Examples 1 and 2, the absorption capacity and the liquid return amount were measured by the following methods in order to evaluate the absorption performance and the liquid return prevention property. Moreover, the softness | flexibility and fitting property were evaluated by the method shown below. The results are shown in Table 2.

Thereafter, the measurement related to the performance was measured at n = 3, and the average value was taken as the measured value.
[Absorption performance]
Materials other than the absorbers of Examples 1 to 6 and Comparative Examples 1 and 2 created in a size of 400 mm in length and 100 mm in width, and a commercially available disposable diaper (Mary's M size) manufactured by Kao Corporation Therefore, a disposable diaper having the same structure as the disposable diaper was prepared and used as an evaluation sample.
In the evaluation, the sample was fixed to a 30 ° inclined plate so that the width direction was up and down, and 40 g of physiological saline was repeatedly injected at intervals of 5 minutes at a position 20 mm from the upper end of the absorber. The liquid from the end of the absorber (if the sample gets over the three-dimensional gather and leaks from the width direction end, or the liquid is dammed by the three-dimensional gather and may leak from the longitudinal end) The amount of injection until leaking out was compared.
The evaluation result was calculated by using the following formula to calculate the relative value when the absorption capacity of Example 1 was 1.0.
Absorption capacity (relative value) = (absorption capacity of sample) / (absorption capacity of Example 1)

[Liquid returnability]
A test sample was prepared in the same manner as the evaluation of the absorption performance described above.
A cylinder having an inner diameter of 35 mm was placed in the center in the width direction at 200 mm from the front end in the longitudinal direction of the absorbent body, and 40 g of physiological saline was injected while maintaining the liquid so that the height was 10 mm. At this time, the time required for absorption was measured. 10 minutes after the start of absorption, 40 g was injected again and the absorption time was measured, and the same operation was repeated three times in total to absorb a total of 120 g of physiological saline. In the evaluation of the absorption time, the time required for the third absorption is taken as the evaluation value, and the shorter the time, the better the performance.
Prepare a filter paper (Advantech No. 5A) cut to 100 mm x 100 mm in advance and 30 sheets in layers (weight measurement W1), and 10 minutes after the start of injection, place it on the absorber centering on the injection point. A pressure of 3.5 kPa was applied through an acrylic plate having a thickness of 5 mm and 100 mm × 100 mm, and the weight of the filter paper was measured after 2 minutes (W2), and the liquid return amount was calculated according to the following equation.
Liquid return amount (g) = weight of first filter paper (W1) −weight of filter paper after pressurization (W2)

[Flexibility]
The absorber was subjected to a handle-ometer test, and the flexibility was evaluated according to the following criteria. The smaller the value, the better the contactability and fit.
A: The measured value of the handle o meter is 0.5 N or less.
○: The measured value of the handle-o-meter exceeds 0.5N and is 1N or less.
(Triangle | delta): The measured value of a handle-ometer exceeds 1N and is 1.5N or less.
X: The measured value of the handleometer exceeds 1.5N.

[Fit (discomfort due to swelling)]
A disposable diaper having the same structure as that of the disposable diaper was prepared using each of the obtained absorbents and other materials excluding the absorbent of a commercially available disposable diaper (Merry's Pants L size) manufactured by Kao Corporation. The prepared diapers were attached to 5 infants (7 to 14 months) using L size pants diapers, and their mother's impressions were heard including after peeing. For the pants diaper, a diaper having the same structure was prepared by using other materials except the absorbent body of the size of the Merry's pants L (specifications that are commercially available at the time of application).
〔Evaluation criteria〕
○: It fits neatly and the crotch is not stiff.
Δ: A little clear.
X: There is a feeling of muffledness, it is not refreshing, and it does not fit.

Using each of the absorbers of Example 7 and Comparative Example 3 created to have a width of 80 mm and a length of 210 mm, other materials are used except for the absorber of a sanitary napkin (Super Slim Guard Daytime Napkin) manufactured by Kao Corporation. A sanitary napkin having the same structure as that of the sanitary napkin was prepared. The following evaluation was performed using defibrinated horse blood.
A hole with an inner diameter of 10 mm was made in the center of a 3 mm thick acrylic plate having the same area as the absorber, and a cylinder with an inner diameter of 15 mm was set up so as to cover the periphery.
Weights were placed on both ends of the acrylic plate so as to have a load of 5 g / cm 2 each. Inject 6g of defibrinated horse blood (Nippon Biotest Co., Ltd., adjust the viscosity to 8cP as appropriate) into the cylindrical part in about 1 second, measure the time for all defibrinated horse blood to be absorbed, Was divided by the time required for absorption to determine the absorption rate. The state was maintained for 3 minutes after absorption. Next, the acrylic plate and the weight were removed, and 10 sheets of absorbent paper (commercial tissue paper) having a basis weight of 30 g / m ² and a basis weight of 30 g / m ² were placed on the skin contact surface of the sanitary napkin. Further, a weight was placed thereon so that the pressure was 660 Pa, and the pressure was applied for 2 minutes. After pressurization, 10 sheets of absorbent paper were taken out and the weight of the absorbent paper before and after pressurization was measured to determine the amount of blood absorbed by the absorbent paper. This value was defined as the amount of blood returned from the sanitary napkin.

The measured absorption rate and liquid return amount were evaluated in three stages according to the following evaluation criteria, and the results are shown in Table 3.
〔Evaluation criteria〕
Absorption rate ○: 0.15 g / second or more Δ: 0.1 g / second or more and less than 0.15 g / second ×: Less than 0.1 g / second Liquid return amount ○: less than 1.0 g Δ: 1.0 g or more and 1.2 g Less than x: 1.2g or more

It is a top view which partially fractures | ruptures and shows the skin contact surface side (surface sheet side) in the expansion | deployment state of the disposable diaper which is 1st Embodiment of this invention. It is the expanded sectional view which showed typically the II cross section of FIG. It is sectional drawing which shows typically the cross section along the width direction of the sanitary napkin which is 2nd Embodiment of this invention. It is a perspective view which shows the sanitary napkin which is 3rd Embodiment of this invention. It is the expanded sectional view which showed typically the II-II line cross section of FIG.

Explanation of symbols

1 disposable diaper (absorbent article)
2 Top sheet 3 Absorber 31 Upper absorbent layer 33 Fiber mixture 32 Lower absorbent layer 34 Fiber assembly 35 Upper layer 36 Lower layer 4 Back sheet 10 Water-absorbing polymer 11 Second water-absorbing polymer

Claims (5)

  Absorbency provided with an absorbent comprising a water-absorbing polymer having a liquid flow rate under pressure at 2.0 kPa of 50 ml / min or more and an absorption amount under pressure at 2.0 kPa of less than 25 g / g. Goods.   The absorbent comprises an absorbent layer composed of a fiber mixture of the water-absorbing polymer and a fibrous material, and the fiber mixture has a liquid flow rate under pressure of 2.0 kPa of 35 ml / min or more. The absorbent article according to claim 1.   The said absorber has the upper absorption layer which consists of a fiber mixture of the said water absorbing polymer and a fibrous material, and the lower absorption layer distribute | arranged to the non-skin contact surface side of this upper absorption layer, or 2. The absorbent article according to 2.   The absorbent article according to claim 1 or 2, wherein the absorbent body has a lower layer and an upper layer having liquid permeability, and the water-absorbing polymer is sandwiched between the lower layer and the upper layer.   The absorbent article according to any one of claims 1 to 4, wherein the water-absorbing polymer is surface-treated with particles having a particle size distribution having different particle sizes.

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